Quantum dots, production methods thereof, and electronic devices including the same

ABSTRACT

An electronic device includes, a light source having a peak emission at a wavelength between about 440 nm to about 480 nm; and a photoconversion layer disposed on the light source,
         wherein the photoconversion layer includes a first quantum dot which emits red light and a second quantum dot which emits green light,   wherein at least one of the first quantum dot and the second quantum dot has a perovskite crystal structure and includes a compound represented by Chemical Formula 1:       

       AB′X 3αα   Chemical Formula 1
         wherein A is a Group IA metal, NR 4   + , or a combination thereof, B′ is a Group IVA metal, X is a halogen, BF 4   − , or a combination thereof, and α is 0 to 3.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 15/393,632, filed on Dec. 29, 2016, which claimspriority to and the benefit of Korean Patent Application No.10-2015-0189007, filed in the Korean Intellectual Property Office onDec. 29, 2015, and all the benefits accruing therefrom under 35 U.S.C. §119, the entire contents of which in their entirety are incorporatedherein by reference.

BACKGROUND 1. Field

Electronic devices including a quantum dot are disclosed.

2. Description of the Related Art

Nanoparticles have many intrinsic physical characteristics (e.g., energybandgaps and melting points) that may be controlled by changing theirparticle size. For example, a semiconductor nanocrystal, also known as aquantum dot, is a type of a semiconductor material having a crystallinestructure with a size of several nanometers. The quantum dot has such asmall size that they may have a large surface area per unit volume,thereby showing a quantum confinement effect. The quantum dot hasdifferent physicochemical characteristics from those of a bulk material.For example, the quantum dot may absorb light from an excitation sourceto reach an excited state and subsequently emit energy (e.g., light)corresponding to its energy bandgap.

In the quantum dot, the energy bandgap may be adjusted by controllingthe size and/or the composition of the nanocrystal and thereby it mayemit light of various wavelengths.

The quantum dot may have a theoretical quantum yield (QY) of about 100%and may emit light of high color purity (e.g., light having a full widthhalf maximum of about 40 nanometers (nm)). The quantum dot may realizeenhanced luminous efficiency and improved color reproducibility.Therefore, research has been conducted with regard the use of thequantum dot in different electronic devices such as a display device(e.g., an LCD), a lighting installation, and the like. Despite thisresearch, there remains a need for electronic devices including quantumdots having improved properties.

SUMMARY

An embodiment provides an electronic device (e.g., a backlight unit, aliquid crystal display device, and the like) having enhanced luminousproperties (e.g., color reproducibility).

In an embodiment, an electronic device includes a light source having apeak emission at a wavelength between about 440 nanometers (nm) to about480 nm; and a photoconversion layer disposed on the light source,wherein the photoconversion layer includes a first quantum dot whichemits red light and a second quantum dot which emits green light,wherein at least one of the first quantum dot and the second quantum dothas a perovskite quantum dot having a perovskite crystal structure andthe perovskite quantum dot includes a compound represented by ChemicalFormula 1:

AB′X_(3+α)  Chemical Formula 1

wherein A is a Group IA metal selected from Rb, Cs, Fr, and acombination thereof, NR₄ ⁺, wherein each R is independently a hydrogenatom or a substituted or unsubstituted C1 to C10 straight chain orbranched chain alkyl group, [CH(NH₂)₂]⁺, or a combination thereof; B′ isa Group IVA metal selected from Si, Ge, Sn, Pb, and a combinationthereof; X is a halogen selected from F, Cl, Br, I, and a combinationthereof, BF₄ ⁻, or a combination thereof, and α is 0 to 3.

A peak emission wavelength of the red light may be between about 620 nmand about 650 nm and a peak emission wavelength of the green light maybe between about 500 nm and about 550 nm.

At least one of the first quantum dot and the second quantum dot may bea non-perovskite quantum dot not having a perovskite crystal structureand the non-perovskite quantum dot may include a Group II-VI compound, aGroup III-V compound, a Group IV-VI compound, a Group IV element, aGroup IV compound, a Group I-III-VI compound, a Group I-II-IV-VIcompound, or a combination thereof.

The perovskite quantum dot may further include at least one of a firstdopant and a second dopant, wherein the first dopant may includepotassium (K) or a first metal having a crystal ionic radius of lessthan about 133 picometers (pm) and being different from the Group IVAmetal and the Group IA metal and, if present, and the second dopant mayinclude a non-metal element which forms a bond with the Group IVA metal.

The first metal may have a crystal ionic radius that is smaller than acrystal ionic radius of the Group IVA metal in the compound of Chemical

Formula 1.

The first metal may include Zn, Cd, Hg, Ga, In, Tl, Cu, Al, Li, Na, Be,Mg, Ca, Sr, Ag, Pt, Pd, Ni, Co, Fe, Cr, Zr, Mn, Ti, Ce, Gd, or acombination thereof.

In an embodiment, the non-metal element includes S, Se, Te, or acombination thereof.

The perovskite quantum dot may include the first dopant, and an amountof the first dopant may be greater than or equal to about 0.001 partsper million (ppm) as measured by inductively coupled plasma-atomicemission spectroscopy (ICP-AES).

The perovskite quantum dot may include the second dopant, and an amountof the second dopant may be greater than or equal to about 0.001 ppm asmeasured by inductively coupled plasma-atomic emission spectroscopy(ICP-AES).

The perovskite quantum dot may include the first dopant and the seconddopant and each of an amount of the first dopant and an amount of thesecond dopant may be greater than or equal to about 0.001 ppm asmeasured by inductively coupled plasma-atomic emission spectroscopy(ICP-AES).

The compound represented by Chemical Formula 1 may include CsPbCl_(3+α),CsPbBr_(3+α), CsPbI_(3+α), CsPb(Cl,I)_(3+α), CsPb(Br,I)_(3+α),CsPb(Br,Cl)_(3+α), or a combination thereof.

In the perovskite quantum dot, an atomic ratio of a halogen to the GroupIA metal may be greater than or equal to about 3.0 as measured bytransmission electron microscope-energy dispersive X-ray spectroscopy(TEM-EDX).

In the perovskite quantum dot, an atomic ratio of a halogen to the GroupIA metal may be greater than or equal to about 3.1 as measured bytransmission electron microscope-energy dispersive X-ray spectroscopy(TEM-EDX).

At least one of the first quantum dot and the second quantum dot mayindependently include an organic ligand compound on a surface thereof,wherein the organic ligand compound is at least one selected from RCOOH,RNH₂, R₂NH, R₃N, RSH, R₃PO, R₃P, ROH, RCOOR′, RPO(OH)₂, R₂POOH, RCOOCOR′(wherein, R and R′ are independently a substituted or unsubstituted C1to C24 aliphatic hydrocarbon group or a substituted or unsubstituted C5to C24 aromatic hydrocarbon group), and a combination thereof.

The photoconversion layer may include a polymer matrix and the firstquantum dot and the second quantum dot may be dispersed in the polymermatrix.

The polymer matrix may include a thiolene polymer, a(meth)acrylate-based polymer, a urethane-based polymer, an epoxypolymer, a vinyl-based polymer, a silicone polymer, or a combinationthereof.

The electronic device is configured to emit light which may have a colorgamut ratio of at least about 80% with respect to BT2020 in a CIE1931color space.

The electronic device is configured to emit light which may have a colorgamut ratio of at least about 87% with respect to BT2020 in a CIE1931color space.

The electronic device is configured to emit light which may have a colorgamut ratio of at least about 88% with respect to BT2020 in a CIE1931color space.

The device is configured such that green light emitted from thephotoconversion layer has a color coordinate Cy value of greater than orequal to about 0.73.

The electronic device may further include a liquid crystal panel, andthe liquid crystal panel may include a lower substrate, an uppersubstrate, and a liquid crystal layer interposed between the upper andlower substrates.

The liquid crystal panel may include an absorption color filter, thephotoconversion layer is configured to emit white light, and the liquidcrystal panel may be disposed on the photoconversion layer so that thewhite light passes through the liquid crystal panel.

In some embodiments, the absorption color filter may have a first colorsection configured for passing red light, a second color sectionconfigured for passing green light, and a third color section configuredfor passing blue light, wherein a light emitted from the photoconversionlayer and passing through the second color section has a spectrum whichmay not include an emission peak having a normalized intensity ofgreater than or equal to about 0.1 at a wavelength of less than about500 nm, and wherein a light emitted from the photoconversion layer andpassing through the third section has a spectrum which may not includeemission peak having an a normalized intensity of greater than or equalto about 0.15 at a wavelength of greater than about 500 nm.

In some embodiments, the liquid crystal panel does not include anabsorption color filter, and the photoconversion layer may be disposedon a top surface or a bottom surface of the upper substrate of theliquid crystal panel.

The photoconversion layer may have a pattern including a first colorsection configured to emit red light, a second color section configuredto emit green light, and a third color section configured to pass oremit blue light.

The red light may have a maximum peak emission wavelength of about 620nm to about 650 nm and the green light may have a maximum peak emissionwavelength of about 530 nm to about 550 nm

The first color section may include the first quantum dot and the secondcolor section may include the second quantum dot

The electronic device of the aforementioned embodiments may have anincreased color reproduction range and thus may have a higher colorgamut ratio with respect to a BT2020 standard in a CIE 1931 color space.

In some embodiments, an electronic device includes:

a light source having a peak emission at a wavelength of about 440 nm toabout 480 nm; and

a photoconversion layer disposed on the light source,

wherein the photoconversion layer comprises a first quantum dot and asecond quantum dot different from the first quantum dot, and the firstquantum dot and the second quantum dot are configured to convert thewavelength of light emitted from the light source into light having awavelength which is different from the wavelength of light emitted fromthe light source, and wherein the device is configured to emit lighthaving a color gamut ratio of at least about 80% with respect to BT2020in a CIE1931 color space.

In the electronic device, at least one of the first quantum dot and thesecond quantum dot may have a perovskite crystal structure and includesa compound represented by Chemical Formula 1:

AB′X_(3+α)  Chemical Formula 1

wherein A is a Group IA metal selected from Rb, Cs, Fr, and acombination thereof, NR₄ ⁺, wherein each R is independently a hydrogenatom or a substituted or unsubstituted C1 to C10 straight chain orbranched chain alkyl group, [CH(NH₂)₂]⁺, or a combination thereof; B′ isa Group IVA metal selected from Si, Ge, Sn, Pb, and a combinationthereof; X is a halogen selected from F, Cl, Br, I, and a combinationthereof, BF₄ ⁻, or a combination thereof, and α is 0 to 3.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, advantages and features of this disclosurewill become more apparent by describing in further detail exemplaryembodiments thereof with reference to the accompanying drawings, inwhich:

FIG. 1 is a flowchart of a method of manufacturing a perovskite quantumdot, according to an embodiment;

FIG. 2 is a flowchart of a method of manufacturing a perovskite quantumdot, according to another embodiment;

FIG. 3 is a flowchart of a method of manufacturing a perovskite quantumdot, according to yet another embodiment;

FIG. 4 is a schematic view showing a cross-section of a quantumdot-polymer composite, according to an embodiment;

FIG. 5 is a schematic view showing a cross-section of an electronicdevice, according to an embodiment;

FIG. 6 is a schematic view showing a cross-section of a liquid crystaldisplay (“LCD”), according to another embodiment;

FIG. 7 is a schematic view showing a cross-section of a LCD, accordingto still another embodiment;

FIG. 8 is a schematic view showing a cross-section of a LCD, accordingto still another embodiment;

FIG. 9 is a schematic view showing a cross-section of a LCD, accordingto still yet another embodiment;

FIG. 10 is a schematic view showing a cross-section of a LCD, accordingto another embodiment;

FIG. 11 is a chromaticity diagram of color coordinate values (Cx, Cy),showing various standards for evaluating a color gamut ratio in a CIEcolor space across a color reproduction range;

FIG. 12 is a graph of intensity (arbitrary units, a.u.) versuswavelength (nm), showing the light emission spectrum of a deviceprepared in accordance with Comparative Example 1;

FIG. 13 is graph of intensity (a.u.) versus wavelength (nm), showing thelight emission spectrum of a device prepared in accordance with Example1;

FIG. 14 is a chromaticity diagram of color coordinate values (Cx, Cy)showing a color gamut with respect to BT2020 standard for each of thedevices prepared in accordance with Comparative Example 1 and Example 1;

FIG. 15 is a chromaticity diagram of chromaticity coordinates (Cx, Cy)having a Cy value of greater than or equal to about 0.65 and a Cx valueof 0.10 to 0.30, and showing a color gamut with respect to BT2020standard for each of the devices prepared in accordance with ComparativeExample 1 and Example 1;

FIG. 16 is a chromaticity diagram of color coordinate values (Cx, Cy)and showing a color gamut with respect to BT2020 standard for each ofthe devices prepared in accordance with Comparative Example 2 andExample 1;

FIGS. 17 to 19 are graphs of intensity (au) versus wavelength (nm),showing the red, green, and blue (RGB) spectrums of the device ofExample 1, respectively;

FIGS. 20 to 22 are graphs of intensity (au) versus wavelength (nm),showing the RGB spectrums of the device of Example 2, respectively;

FIG. 23 is a graph of transmittance versus wavelength (nm), showing thelight transmission spectrums of the red color filter used in Example 1and the red color filter used in Comparative Example 2;

FIG. 24 is a graph of transmittance versus wavelength (nm), showing thelight transmission spectrums of the green color filter used in Example 1and the green color filter used in Comparative Example 2;

FIG. 25 is a graph of transmittance versus wavelength (nm), showing thelight transmission spectrums of the blue color filter used in Example 1and the blue color filter used in Comparative Example 2;

FIG. 26 is a graph of intensity (au) versus wavelength (nm), showing alight emission spectrum of the device prepared in accordance withExample 2;

FIG. 27 is a graph of intensity (au) versus wavelength (nm), showing alight emission spectrum of the device prepared in accordance withComparative Example 4;

FIG. 28 is a chromaticity diagram of color coordinate values (Cx, Cy)showing a color gamut with respect to BT2020 standard for each of thedevices prepared in accordance with Comparative Example 4 and Example 2;

FIG. 29 is a chromaticity diagram of color coordinate values (Cx, Cy)having a Cy value of greater than or equal to about 0.65 and a Cx valueof 0.10 to 0.30, showing a color gamut with respect to BT2020 standardfor each of the devices prepared in accordance with Comparative Example4 and Example 2;

FIGS. 30 to 32 are graphs of intensity (au) versus wavelength (nm)showing the RGB spectrums of the device of Example 2, respectively;

FIG. 33 is a graph of intensity (au) versus wavelength (nm), showing alight emission (RGB) spectrum of the device of Comparative Example 3;

FIG. 34 is a chromaticity diagram of color coordinate values (Cx, Cy)showing a color gamut with respect to BT2020 standard for each of thedevices prepared in accordance with Comparative Example 3 and Example 1;

FIG. 35 is a graph of intensity (au) versus wavelength (nm), showing alight emission (RGB) spectrum of the device of Comparative Example 5;

FIG. 36 is a chromaticity diagram of color coordinate values (Cx, Cy)showing a color gamut with respect to BT2020 standard for each of thedevices prepared in accordance with Comparative Example 5 and Example 2;

FIG. 37 is a flow diagram of an exemplary process of manufacturing aquantum dot-polymer composite based color filter (e.g., a patternedlight conversion layer).

DETAILED DESCRIPTION

Advantages and characteristics of this disclosure, and a method forachieving the same, will become evident referring to the followingexample embodiments together with the drawings attached hereto. Theembodiments may, however, be embodied in many different forms and shouldnot be construed as being limited to the embodiments set forth herein.If not defined otherwise, all terms (including technical and scientificterms) in the specification may be defined as commonly understood by oneskilled in the art. The terms defined in a generally-used dictionary maynot be interpreted ideally or exaggeratedly unless clearly defined.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms, including “at least one,” unless the content clearly indicatesotherwise. “Or” means “and/or.” As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items. In addition, unless explicitly described to the contrary,the word “comprise” and variations such as “comprises” or “comprising,”will be understood to imply the inclusion of stated elements but not theexclusion of any other elements.

Further, the singular includes the plural, unless mentioned otherwise.

It will be understood that, although the terms “first,” “second,”“third” etc. may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are only used to distinguish one element, component, region,layer or section from another element, component, region, layer orsection. Thus, “a first element,” “component,” “region,” “layer” or“section” discussed below could be termed a second element, component,region, layer or section without departing from the teachings herein.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

“About” or “approximately” as used herein is inclusive of the statedvalue and means within an acceptable range of deviation for theparticular value as determined by one of ordinary skill in the art,considering the measurement in question and the error associated withmeasurement of the particular quantity (i.e., the limitations of themeasurement system). For example, “about” can mean within one or morestandard deviations, or within ±10%, 5% of the stated value.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

As used herein, “doping” refers to the inclusion of a dopant in acrystal structure of a quantum dot. In an exemplary embodiment,inclusion of a dopant in the crystal structure does not substantiallychange the crystal structure and/or may be occur through the formationof a bond (e.g. a chemical or physical bond) between the dopant and acomponent of the quantum dot. For example, a dopant atom (e.g., a metalsuch as Zn or a chalcogen element) may be substituted for an atom in acrystal structure, or may be present in the interstices of a crystallattice. In some embodiments, the dopant element may form a bond with anelement constituting the crystal lattice to form a chemical speciesattached to a surface thereof.

In some embodiments, when the dopant is present in the lattice or as analloy, an X-ray diffraction spectrum of the quantum dot including thedopant may show a crystalline peak that is shifted to a differentdiffraction angle relative to an X-ray diffraction spectrum of thequantum dot without the dopant (i.e., an “undoped” quantum dot). Inother embodiments (e.g., the amount of the dopant is very small), theX-ray diffraction spectrum of a quantum dot including the dopant issubstantially the same as the X-ray diffraction spectrum of an undopedquantum dot. When the dopant is present as a crystal outside of thelattice of the quantum dot, its inherent peak may be detected in anX-ray diffraction spectrum of the doped quantum dot. In an embodiment,the presence of the dopant may be confirmed, for example, by X-rayphotoelectron spectroscopy, energy dispersive X ray spectroscopy,inductively coupled plasma-atomic emission spectroscopy (ICP-AES), or acombination thereof.

As used herein, the terms “quantum yield” (QY) or the term “quantumefficiency (QE), are used to refer to a value determined from aphotoluminescence spectrum, which is obtained by dispersing quantum dotsin an organic solvent (e.g. toluene) and calculating relativephotoluminescence with respect to the photoluminescent peak of anorganic solution of a reference dye (e.g., an ethanol solution ofcoumarin dye, which has an absorption (optical density) at 458 nm of0.1). As used herein, the term “quantum yield (QY)” and the term“quantum efficiency (QE)” have substantially the same meaning and can beused interchangeably.

As used herein, the term “metal” refers to a metallic element such as analkali metal, an alkaline earth metal, a transition metal, and a basicmetal. The term “metal” also includes a semi-metallic element such as Siand the like.

As used herein the term “color gamut ratio” refers to an areaconsistency ratio of a color gamut of a given device to a standard colorgamut. The area consistency ratio is a ratio (S2/S1) of the area (S1) ofthe standard color gamut (e.g., a triangle area) to the area (S2) of thecolor gamut of the given device that overlaps the standard color gamut.

Further, the singular includes the plural, unless mentioned otherwise.

In the drawings, the thickness of layers, films, panels, regions, etc.,are exaggerated for clarity. Like reference numerals designate likeelements throughout the specification.

It will be understood that when an element such as a layer, film,region, or substrate is referred to as being “on” another element, itcan be directly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” another element, there are no intervening elements present.

As the quantum dot has a nano-size, the luminous properties andstability of the quantum dot may be easily affected by the externalenvironment. In addition, the dispersablity of the quantum dot tends tobe insufficient in various mediums. Therefore, despite its uniqueproperties, the application of the quantum dot in devices in whichluminous properties and reliability are desired features, may bedifficult.

In an embodiment, an electronic device includes a light source having apeak emission (e.g., a maximum peak emission) at a wavelength of about440 nm to about 480 nm; and a photoconversion layer disposed on thelight source. The photoconversion layer includes a first quantum dotwhich emits a red light and a second quantum dot which emits a greenlight. A peak emission (e.g., a maximum peak emission) of the red lightmay be at a wavelength of about 620 nm to about 650 nm, for example,about 640 nm to about 650 nm. A peak emission (e.g., a maximum peakemission) of the red light may be at a wavelength of about 500 nm toabout 550 nm, for example, about 510 nm to about 530 nm. At least one ofthe first and second quantum dots includes a perovskite quantum dothaving a perovskite crystal structure. In some embodiments, at least oneof the first and second quantum dots may be a non-perovskite quantum dotthat does not have the perovskite crystal structure. For example, thefirst quantum dot may include a non-perovskite quantum dot and thesecond quantum dot may include a perovskite structure. Hereinafter willbe explained some embodiments wherein the first quantum dot is anon-perovskite quantum dot and the second quantum dot is a perovskitestructure. However, it is not limited thereto.

The first quantum dot may include a Group II-VI compound, a Group III-Vcompound, a Group IV-VI compound, a Group IV element, a Group IVcompound, a Group I-III-VI compound, a Group I-II-IV-VI compound, or acombination thereof. In some embodiments, the first quantum dot does notinclude cadmium.

For example, the Group II-VI compound may be selected from:

a binary element compound selected from CdSe, CdTe, ZnS, ZnSe, ZnTe,ZnO, HgS, HgSe, HgTe, MgSe, MgS, and a combination thereof;

a ternary element compound selected from CdSeS, CdSeTe, CdSTe, ZnSeS,ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS,CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS, and a combinationthereof; and

a quaternary element compound selected from HgZnTeS, CdZnSeS, CdZnSeTe,CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, and acombination thereof.

The Group II-VI compound may further include a Group III metal.

The Group III-V compound may be selected from:

a binary element compound selected from GaN, GaP, GaAs, GaSb, AlN, AlP,AlAs, AlSb, InN, InP, InAs, InSb, and a combination thereof;

a ternary element compound selected from GaNP, GaNAs, GaNSb, GaPAs,GaPSb, AINP, AINAs, AINSb, AIPAs, AIPSb, InNP, InNAs, InNSb, InPAs,InPSb, and a combination thereof; and

a quaternary element compound selected from GaAlNP, GaAlNAs, GaAlNSb,GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP,InAlNAs, InAlNSb, InAlPAs, InAlPSb, and a combination thereof.

The Group III-V compound may further include a Group II metal (e.g.,InZnP).

The Group IV-VI compound may be selected from:

a binary element compound selected from SnS, SnSe, SnTe, PbS, PbSe,PbTe, and a combination thereof;

a ternary element compound selected from SnSeS, SnSeTe, SnSTe, PbSeS,PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, and a combination thereof; and

a quaternary element compound selected from SnPbSSe, SnPbSeTe, SnPbSTe,and a combination thereof.

Examples of the Group compound may include CuInSe₂, CuInS₂, CuInGaSe,and CuInGaS, but are not limited thereto.

Examples of the Group I-II-IV-VI compound may include CuZnSnSe andCuZnSnS, but are not limited thereto.

The Group IV element may include:

a single-element selected from Si, Ge, and a combination thereof; and

The Group IV compound may include:

a binary element compound selected from SiC, SiGe, and a combinationthereof.

The binary element compound, the ternary element compound, or thequaternary element compound may respectively be included in a uniformconcentration in the quantum dot particle or may be included inpartially different concentrations in the same quantum dot particle.

The first quantum dot may have a core-shell structure wherein a firstsemiconductor nanocrystal (a core) is surrounded by a crystalline oramorphous material (e.g. a second semiconductor nanocrystal) that isdifferent from the first semiconductor nanocrystal. The interfacebetween the core and the shell may have a concentration gradient whereinthe concentration of an element in the shell radially changes from anouter surface of the shell towards the inner surface of the shell (e.g.,the concentration decreases towards the core). In addition, the coreshell type quantum dot may have a semiconductor nanocrystal core and amulti-layered shell surrounding the semiconductor nanocrystal core. Thecore and multi-layered shell structure has at least two layers of theshell wherein each layer may be a single composition, an alloy, or theone having a concentration gradient.

In the core-shell type quantum dot, a material of the shell (e.g. thesecond semiconductor nanocrystal) may have a larger energy band-gap thanthe material of the core (e.g. the first semiconductor nanocrystal) formore effectively exhibiting a quantum confinement effect. In case of thecore-shell quantum dot having a multi-layered shell, a band-gap energyof the material of an outer layer of the shell may be greater than theband-gap energy of the material of an inner layer of the shell (a layerthat is closer to the core).

The first quantum dot may have a quantum yield of greater than or equalto about 10 percent (%), or greater than or equal to about 30%, forexample, greater than or equal to about 50%, greater than or equal toabout 60%, greater than or equal to about 70%, or greater than or equalto about 90%. The first quantum dot may have a full width at half max(FWHM) of less than or equal to about 45 nm, for example less than orequal to about 40 nm, or less than or equal to about 30 nm.

The first quantum dot may have a particle size (e.g., a diameter or alongest length) of about 1 nm to about 100 nm. For example, the firstquantum dot may have a particle diameter of about 1 nm to about 20 nm,for example, from 2 nm to 15 nm, or from about 3 nm to about 15 nm.

The shape of the first quantum dot is not particularly limited. Forexample, the quantum dot may include a nanosized particle or ananosheet. The first quantum dot may have a spherical shape, ellipticalshape, pyramidal shape, polygonal shape, multi-armed shape, or a cubicshape.

The first quantum dot is commercially available or may be synthesized byany method known in the art. For example, several nano-sized quantumdots may be synthesized according to a wet chemical process. In the wetchemical process, precursors react in an organic solvent to grownanocrystal particles, and the organic solvent or a ligand compound maycoordinate to the surface of the nanocrystal particle, therebycontrolling a growth thereof.

The perovskite quantum dot (e.g., the second quantum dot) has aperovskite crystal structure and includes a compound represented byChemical Formula 1:

AB′X_(3+α)  Chemical Formula 1

wherein A is a Group IA metal selected from Rb, Cs, Fr, and acombination thereof, NR₄ ⁺, wherein each R is independently a hydrogenatom or a substituted or unsubstituted C1 to C10 straight chain orbranched chain alkyl group, [CH(NH₂)₂]+, or a combination thereof; B′ isa Group IVA metal selected from Si, Ge, Sn, Pb, and a combinationthereof; X is at least one halogen selected from F, Cl, Br, and I, BF₄⁻, or a combination thereof, and a is greater than or equal to 0, forexample, greater than 0, greater than or equal to about 0.1, or greaterthan or equal to about 0.2, and less than or equal to about 3 forexample, less than or equal to about 2.5, less than or equal to about 2,less than or equal to about 1.5, less than or equal to about 1, lessthan or equal to about 0.9, less than or equal to about 0.8, less thanor equal to about 0.7, less than or equal to about 0.6, less than orequal to about 0.5, less than or equal to about 0.4, or less than orequal to about 0.3. In an embodiment, a surface of the quantum dotincludes a halogen. For example, NR₄ ⁺ may be [CH₃NH₃]⁺, NH₄ ⁺,[C₂H₅NH₃]⁺, or a combination thereof.

The compound represented by Chemical Formula 1 may include CsPbCl_(3+α),CsPbBr_(3+α), CsPbI_(3+α), CsPb(Cl,I)_(3+α), CsPb(Br,I)_(3+α),CsPb(Br,Cl)_(3+α), or a combination thereof. As used herein, theexpression (X1, X2) (wherein X1 and X2 are each independently a halogendifferent from each other, such as (Cl,I), (Br,I), and (Br,I), refers toa compound that includes two different halogens (e.g., Cl and I, Br andI, or Br and Cl). When the compound includes two halogens, the moleratio therebetween is not particularly limited. For example, when thecompound includes two halogens, X1 and X2, the amount of the X2 per onemole of X1 is greater than or equal to about 0.01 moles, for example,0.1 moles, greater than or equal to about 0.2 moles, greater than orequal to about 0.3 moles, greater than or equal to about 0.4 moles, orgreater than or equal to about 0.5 moles. In an embodiment, when thecompound includes two halogens, X1 and X2, the amount of the X2 per onemole of X1 is less than or equal to about 100 moles, less than or equalto about 10 moles, less than or equal to about 9 moles, less than orequal to about 8 moles, less than or equal to about 7 moles, less thanor equal to about 6 moles, less than or equal to about 5 moles, lessthan or equal to about 4 moles, less than or equal to about 4 moles,less than or equal to about 3 moles, less than or equal to about 2moles, or less than or equal to about 1 mole. For example, when thecompound includes two halogens, X1 and X2, the amount of the X2 per onemole of X1 is about 0.1 moles to about 10 moles, about 0.2 moles toabout 5 moles, or about 0.3 moles to about 3 moles, but it is notlimited thereto.

The perovskite crystal structure may have a cubic crystalline latticeand the presence thereof can be confirmed by X-ray diffractionspectroscopy. In the embodiments, the second quantum dot may have acubic shape and/or a rectangular parallelepiped shape, but it is notlimited thereto. The second quantum dot may have a core-shell structure.Details of the core-shell structure are the same as set forth above.

In the second quantum dot, an atomic ratio of a halogen element to theGroup IA element as measured by transmission electron microscope-energydispersive X-ray spectroscopy (TEM-EDX) may be greater than or equal toabout 3.0, for example, greater than or equal to about 3.1. The secondquantum dot may include a greater amount of halogen than astoichiometric amount for the formation of the perovskite crystal and/ora surface of the quantum dot may have a halogen rich surface.

The perovskite quantum dot may further include at least one of a firstdopant and a second dopant. The second dopant may include a non-metalelement that forms a bond with the Group IVA metal. The first dopant mayinclude potassium (K) or a first metal having a crystal ionic radius ofless than about 133 picometers (pm) and being different from the GroupIVA metal and, if present, the Group IA metal. For example, the firstmetal may have a crystal ionic radius of about 67 pm to about 120 pm.The first metal may have a crystal ionic radius that is less than thecrystal ionic radius of the Group IVA metal of the component B inChemical Formula 1. For example, when B is Pb, the crystal ionic radiusof the first metal is less than 133 pm. The crystal ionic radius maycorrespond to the physical size of the ion in a solid, and in thisregard, the publication of the revised ionic radius by Shannon may bereferred to (e.g., R. D. Shannon (1976) “Revised effective ionic radiiand systematic studies of interatomic distances in halides andchalcogenides”. Acta Cryst A32, pp. 751-767, the content of which isincorporated herein by reference in its entirety).

The first dopant may substitute for the metal element (e.g., the GroupIA metal such as Cs and Rb, and/or the Group IVA metal such as Pb) inthe compound represented by Chemical Formula 1. In an embodiment, thefirst dopant may include the first metal having a crystal ionic radiusthat is less than crystal ionic radius of the Group IVA element. In anembodiment, the first dopant may include a metal ion (e.g., a monovalention or a divalent ion) having the same valence as that of the Group IVAmetal or a Group IA metal. In an embodiment, the first dopant mayinclude a metal capable of forming a compound (e.g., a metal oxide)having a lattice structure that is substantially similar to that of theperovskite lattice structure. The second dopant may include an elementthat may form a chemical bond with the Group IVA metal (e.g., Pb) duringthe synthesis of a quantum dot including the aforementioned compound,and thereby may be precipitated out of solution. Without wishing to bebound by theory, it is believed that this may contribute to decreasingthe amount of the Group IVA metal in a reaction system during thesynthesis. As a result, the resulting quantum dot may include an excessamount of the halogen, or a surface of the quantum dot may include ahalogen.

In some embodiments, the first metal may be selected from Zn, Cd, Hg,Ga, In, Tl, Cu, Al, Li, Na, Be, Mg, Ca, Sr, Ag, Pt, Pd, Ni, Co, Fe, Cr,Zr, Mn, Ti, Ce, Gd, and a combination thereof. In some embodiments, thenon-metal element may be selected from S, Se, Te, and a combinationthereof.

The presence of the first and second dopants may be confirmed byinductively coupled plasma-atomic emission spectroscopy (ICP-AES). Forexample, in the quantum dot, the amount of the first dopant may begreater than or equal to about 0.001 ppm, for example, greater than orequal to about 0.04 ppm, as measured by ICP-AES. In the quantum dot, theamount of the second dopant may be greater than or equal to about 0.001ppm, for example, about 0.04 ppm as measured by ICP-AES.

The first and second quantum dots may be a colloidal quantum dotprepared using a wet chemical method, and thus a surface thereof mayhave an organic ligand compound. The organic ligand compound may beselected from RCOOH, RNH₂, R₂NH, R₃N, RSH, R₃PO, R₃P, ROH, RCOOR′,RPO(OH)₂, R₂POOH, RCOOCOR′, and a combination thereof, wherein, each Rand R′ are independently a substituted or unsubstituted C1 to C24aliphatic hydrocarbon group such as an alkyl group, an alkenyl group, oran alkynyl group, or a substituted or unsubstituted C5 to C24 aromatichydrocarbon group, such as an aryl group.

Specific examples of the organic ligand compound may include methanethiol, ethane thiol, propane thiol, butane thiol, pentane thiol, hexanethiol, octane thiol, dodecane thiol, hexadecane thiol, octadecane thiol,benzyl thiol; methane amine, ethane amine, propane amine, butane amine,pentane amine, hexane amine, octane amine, dodecane amine, hexadecylamine, octadecyl amine, dimethyl amine, diethyl amine, dipropyl amine,oleylamine, methanoic acid, ethanoic acid, propanoic acid, butanoicacid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid,dodecanoic acid, hexadecanoic acid, octadecanoic acid, oleic acid,benzoic acid, palmitic acid, stearic acid; a phosphine such as methylphosphine, ethyl phosphine, propyl phosphine, butyl phosphine, pentylphosphine, tributylphosphine, or trioctylphosphine; a phosphine compoundor an oxide compound thereof such as methyl phosphine oxide, ethylphosphine oxide, propyl phosphine oxide, butyl phosphine oxide, ortrioctylphosphine oxide; diphenyl phosphine, triphenyl phosphine or anoxide compound thereof; phosphonic acid, and the like, but are notlimited thereto. The organic ligand compound may be used alone or as amixture of greater than two organic ligands.

In some embodiments, the quantum dot does not include an amine organicligand having an alkyl group of at least 6 carbon atoms, such as atleast 8 carbon atoms (e.g., n-octyl amine).

A colloidal halide perovskite quantum dot may be an example of asuitable quantum dot material due to its photoluminescence propertiessuch as color tunability, desirable bandgap, and the like. For example,a CsPbX₃ nanoparticle and a CH₃NHPbX₃ nanoparticle are examples of afully or partially inorganic perovskite nanoparticle.

The inventors have found that the halide perovskite quantum dot of, forinstance, a CsPbX₃ nanoparticle or a CH₃NHPbX₃ nanoparticle, does nothave desirable stability. For example, the halide perovskite quantum dotmay exhibit an undesirable quantum yield when separated from a synthesissolvent and/or washed to remove the solvent, or after dispersion in adispersion solvent (e.g., toluene). In addition, the dispersability ofthe halide perovskite quantum dot may decrease over time. For example,when the halide perovskite quantum dot is separated from the synthesissolvent thereof, dispersed in a dispersion solvent such as toluene, andthen allowed to stand in the air, it loses its photoluminescence withinone week, and is precipitated.

Without wishing to be bound by any theory, it is believed that when thehalide perovskite quantum dot is separated from the synthesis solventand washed, the quantum dot may lose an amount of an organic ligandpreviously bound to a surface thereof, and due to the loss of theligand, the metal elements may be exposed on a surface thereof. Theexposed metal elements may be susceptible to factors in the externalenvironment such as oxygen, moisture, or heat, and as a result, themetal elements may be transformed into an oxide or a decompositionproduct. However, rather than being used directly after the synthesis,the quantum dots may be washed with a non-solvent for the removal ofimpurities, and then re-dispersed in a solvent optimized for an appliedfield. In addition, the quantum dots may go through a surface exchangeor may be prepared into a quantum dot-polymer composite. Theaforementioned changes on a surface of the quantum dot (i.e., loss ofthe ligand and exposure of a metal atom) which occur after the washingwith the non-solvent, and the subsequent deterioration in stabilitycaused thereby, may hinder the subsequent application of the quantumdot.

In some embodiments, the perovskite quantum dot may include a firstdopant such as Zn and/or a second dopant such as Se and/or may include ahalogen in an amount greater than the amount necessary for the formationof the perovskite structure. Accordingly, the second quantum dot mayavoid a substantial decrease in quantum efficiency (or quantum yield)when removed from a synthesis solvent, washed, and then dispersed againin a dispersion solvent. For example, after being separated from thesynthesis solvent, the second quantum dot may have a quantum efficiencyof greater than or equal to about 60%, for example, greater than orequal to about 70%, greater than or equal to about 75%, or greater thanor equal to about 80%, relative to its original quantum efficiency. Inaddition, the second quantum dots may be stable with respect to anexternal environment such as oxygen, moisture, and the like when theyare dispersed in a dispersion solvent (e.g., toluene). For example, thequantum dot of an embodiment may maintain initial quantum efficiencyafter being in air for about 24 hours or longer, or about 48 hours orlonger. In addition, the second quantum dot may include a surface ligandin at least an amount necessary for maintaining its stability, evenafter they are separated from the synthesis solvent and washed.Therefore, the second quantum dot may be re-dispersed in variousdifferent types of dispersion solvents even after being kept in the air.

Without wishing to be bound by any theory, it is believed that thesecond quantum dot having a perovskite structure may include an excessamount of a halogen, optionally together with a first dopant and/or asecond dopant, on a surface thereof and thereby its entire compositionand/or surface composition may change to keep the ligand loss at aminimum level (e.g., suppress ligand loss) upon the washing with thenon-solvent. In addition, an individual or combined effect of thehalogen element, the first/second dopant(s), and the ligand on a surfacethereof may suppress oxidation of the metal constituting the perovskitestructure, thereby preventing damage to the perovskite structure.

The second quantum dot may have a size of about 1 nm to about 50 nm, forexample, about 2 nm to about 15 nm, or about 3 nm to about 14 nm. Thesize of the quantum dot may be measured using any suitable method. Forexample, the size of the quantum dot may be directly measured from atransmission electron microscopic (TEM) image or may be calculated fromthe full width at half maximum (FWHM) of the peak of the XRD spectrumusing the Scherrer equation. The second quantum dot may have a FWHM of aphotoluminescence peak wavelength of less than or equal to about 30 nm,for example, less than or equal to about 29 nm, less than or equal toabout 28 nm, less than or equal to about 27 nm, less than or equal toabout 26 nm, or less than or equal to about 25 nm. The quantum dot mayhave quantum efficiency (QE) or quantum yield (QY) of greater than orequal to about 60%, for example, greater than or equal to about 62%,greater than or equal to about 63%, greater than or equal to about 64%,greater than or equal to about 65%, greater than or equal to about 66%,or greater than or equal to about 67%. The second quantum dot of anembodiment, for example, does not include cadmium, but may showdesirable photoluminescence characteristics (e.g., a high quantumefficiency, a narrow FWHM, desirable color purity, and the like).

The second quantum dot of some embodiments may be prepared by a methodthat includes:

preparing a reaction solution including a first precursor including aGroup IA metal selected from Rb, Cs, Fr, and a combination thereof, NR₄⁺ (wherein each R independently is a hydrogen atom or a substituted orunsubstituted C1 to C10 straight chain or branched chain alkyl group),[CH(NH₂)₂]⁺, BF4, or a combination thereof; a second precursor includinga halogen and a Group IVA metal selected from Ge, Si, Sn, Pb, and acombination thereof; and at least one of a first additive and a secondadditive, wherein the first additive includes a halogen and a firstmetal, the first metal having a crystal ionic radius of less than orequal to about 133 pm and being different from the Group IVA metal and,if present, the Group IA metal, and the second additive includes anon-metal element that may form a bond with the Group IVA metal; and

carrying out a reaction between the first precursor and the secondprecursor in the reaction solution to synthesize a quantum dot that hasa perovskite crystal structure, includes a compound represented byChemical Formula 1, and has a size of about 1 nm to about 50 nm

The halogen may include F, Cl, Br, I, or a combination thereof.

The preparing of the reaction solution may include solvating the firstprecursor, the second precursor, the first additive, the secondadditive, or combination thereof in a solvent selected from a C6 to C22amine compound, a nitrogen-containing heterocyclic compound, a C6 to C40aliphatic hydrocarbon, a C6 to C30 aromatic hydrocarbon, a C6 to C22phosphine oxide compound, a C12 to C22 aromatic ether, and a combinationthereof.

The reaction solution may further include at least one organic ligandcompound selected from RCOOH, RNH₂, R₂NH, R₃N, RSH, R₃PO, R₃P, ROH,RCOOR′, RPO(OH)₂, R₂POOH, RCOOCOR′, and a combination thereof, wherein,each R and R′ are independently a substituted or unsubstituted C1 to C24aliphatic hydrocarbon group or a substituted or unsubstituted C5 to C24aromatic hydrocarbon group.

Referring to FIGS. 1 to 3 illustrating non-limiting examples, thepreparation of a reaction solution is illustrated in more detail.

Referring to FIG. 1, the second precursor (e.g., PbX₂) and the firstadditive (e.g., ZnX₂) are mixed in a solvent, and the organic ligand(e.g., oleylamine and oleic acid) is injected thereinto to prepare asolution of the second precursor and the first additive.

Aside from the preparation of the aforementioned solution, a compoundincluding a Group IA metal (e.g., Cs₂CO₃) or a quaternary ammonium salt(e.g., a [CH(NH₂)₂]⁺ salt or a NR₄ ⁺ salt such as CH₃NH₃Br or CH₃NH₃BF₄)is dissolved in a solvent and optionally a compound (e.g., oleic acid)for forming the first precursor, and the solution is optionally heatedto prepare a first precursor solution including the first precursor(e.g., Cs oleate, that is, Group IA metal-carboxylate or quaternaryammonium salt such as CH₃NH₃Br).

The first precursor solution is added to a solution including the secondprecursor and the first additive to obtain a reaction solution, and areaction between the first and the second precursors is carried out inthe reaction solution. The reaction may be carried out at apredetermined temperature (e.g., at greater than or equal to about 50°C. (e.g., a temperature of about 100° C. to about 240° C.). If desired,the second additive (e.g., selenium-triphenylphosphine (Se-TOP)) may beadded to the reaction solution before the initiation of the reaction orafter the progress of the reaction, and before the completion of thereaction.

Referring to FIG. 2, the second precursor (e.g., PbX₂) may be mixed with(or dissolved in) a solvent, and the organic ligand (e.g., oleylamineand oleic acid) is injected thereto and the second precursor issolubilized to prepare a second precursor-containing solution.

A first precursor solution including the first precursor (e.g., Csoleate, that is, a Group IA metal-carboxylate) may be prepared bydissolving a compound including a Group IA metal (e.g., Cs₂CO₃) in asolvent and optionally a compound for forming the first precursor (e.g.,oleic acid), and optionally heating the solution.

The first precursor solution is added to the second precursor-containingsolution to obtain a reaction solution, and a reaction between the firstand the second precursors is carried out, for example, at a temperatureof greater than or equal to about 50° C. (e.g., a temperature of about100° C. to about 240° C.), and the second additive (e.g., Se-TOP) may beadded to the reaction solution before the initiation of the reaction orafter the progress of the reaction, and before the completion of thereaction. In some embodiments, the first precursor solution may be mixedwith the second precursor-containing solution during a process ofpreparing the second precursor-containing solution or adding materialsfor the second precursor to the first precursor solution in any order.

Referring to FIG. 3, the second precursor (e.g., PbX₂) and the firstadditive (e.g., ZnX₂) are mixed with (dissolved in) a solvent, and theorganic ligand (e.g., oleylamine and oleic acid) is injected thereto todissolve the second precursor and the first additive and thereby asolution including the second precursor and the first additive isprepared. The solution including the first precursor may be prepared inaccordance with the aforementioned manner and may be added to thesolution including the second precursor and the first additive toprovide the reaction solution. As the reaction solution as heated to areaction temperature (e.g., a temperature of greater than or equal toabout 80° C., for example, a temperature of about 100° C. to about 240°C.), a reaction between the first and the second precursors is carriedout to synthesize the second quantum dot.

In the method illustrated in FIGS. 1 to 3, the first additive and thesecond precursor are simultaneously dissolved in a solvent, but themethod is not limited thereto. The first additive may be prepared as aseparate solution from the second precursor and then be added to thereaction solution at any point prior to or during the synthesis of thecompound represented by Chemical Formula 1.

In addition, the second additive may be added to the reaction solutionat any time prior to or during the synthesis of the compound representedby Chemical Formula 1.

As described above, in the aforementioned method, the reaction solutionmay include the first additive, the second additive, or both, before theinitiation of the reaction or added during the progress of the reaction.Accordingly, the reaction solution may include a reduced amount of theGroup IVA metal (e.g. Pb) and a relatively excessive amount of thehalogen.

Without wishing to be bound by any theory, it is believed that in theaforementioned method, the first additive may play a role of providingan additional supply source of the halogen and may contribute toreducing the relative amount of the Group IVA metal in the preparedquantum dot because the metal included therein (e.g., the first metal)may replace the Group IVA metal or may be added separately (e.g.,injected as an interstitial element or bound physically on a surface ofthe quantum dot). In addition, the second additive may form aprecipitate together with the Group IVA metal element (e.g., PbSe)during the synthesis of the compound represented by Chemical Formula 1,and thereby may further reduce the relative amount of the Group IVAmetal element in the quantum dot. Therefore, the second quantum dotprepared according to the aforementioned method may have a halogen richsurface as confirmed by a TEM-EDX analysis without additional processsteps such as a ligand assisted re-precipitation (LARP) process. Inaddition, the quantum dot prepared according to the aforementionedmethod may include the first dopant originated from the first additiveand the second dopant originated from the second additive.

In the aforementioned method, the first precursor includes the Group IAmetal (e.g., Cs or Rb), and may be a metal powder, a metal carbonate, analkylated metal compound, metal alkoxide, metal carboxylate, metalnitrate, metal perchlorate, metal sulfate, metal acetylacetonate, metalhalide, metal cyanide, metal hydroxide, metal oxide, metal peroxide, ora combination thereof. The first precursor may be used alone or as amixture of two or more first precursors.

In some embodiments, the first precursor may include NR₄ ⁺, wherein eachR is independently a hydrogen atom or a substituted or unsubstituted C1to C10 straight or branched alkyl group, such as CH₃NH₃ ⁺, NH₄ ⁺,C₂H₅NH₃ ⁺, HC(NH₂)₂ ⁺, or a combination thereof. The first precursor mayinclude NR₄ ⁺ and BF₄, for example, NR₄ ⁺BF₄ ⁻ such as CH₃NH₃BF₄.

The first precursor may include the one (e.g., Cs-oleate) obtained byreacting a compound (e.g., Cs₂CO₃) including a Group IA metal with acertain compound (e.g., an organic ligand such as oleic acid) in areaction solvent. The first precursor may be heated to a temperature ofgreater than or equal to about 80° C., for example, greater than orequal to about 100° C., before the injection in order to minimizeprecipitation of the first precursor in the reaction solution.

The second precursor may include a Pb halide such as PbCl₂, PbI₂, orPbBr₂, a Ge halide such as GeCl₂, GeCl₄, GeI₂, GeI₂, GeBr₂, or GeBr₄, aSi halide such as SiCl₂, SiCl₄, SiI₂, SiI₄, SiBr₂, SiBr₄, a Sn halidesuch as SnCl₂, SnI₂, or SnBr₂, or a combination thereof. The secondprecursor may be used alone or as a mixture of at least two compounds.For the solubilization of the second precursor, the resulting mixturemay heated at a predetermined temperature of greater than or equal toabout 80° C., for example, greater than or equal to about 120° C., inthe presence of an organic ligand, depending on a selected solvent.

The first additive may include a zinc halide such as ZnCl₂, ZnBr₂, orZnI₂, a Cd halide such as CdCl₂, CdBr₂, or CdI₂, a Hg halide such asHgCl₂, HgBr₂, or HgI₂, a Ga halide such as GaCl₃, GaBr₃, or Gala, an Inhalide such as InCl₃, InBr₃, or InI₃, a Tl halide such as TlCl, TlBr, orTlI, a Cu halide such as CuCl₂, CuBr₂, or CuI₂, a Al halide such asAlCl₃, AlBr₃, or AlI₃, a Li halide such as LiCl, LiBr, or LiI, a Nahalide such as NaCl, NaBr, or NaI, a K halide such as KCl, KBr, or KI, aBe halide such as BeCl₂, BeBr₂, or BeI₂, a Mg halide such as MgCl₂,MgBr₂, or MgI₂, a Ca halide such as CaCl₂, CaBr₂, or CaI₂, a Sr halidesuch as SrCl₂, SrBr₂, or SrI₂, a Ag halide such as AgCl, AgBr, or AgI, aPt halide such as PtCl₂, PtBr₂, or PtI₂, a Pd halide such as PdCl₂,PdBr₂, or PdI₂, a Ni halide such as NiCl₂, NiBr₂, or NiI₂, a Co halidesuch as CoCl₂, CoBr₂, or CoI₂, a Fe halide such as FeCl₂, FeBr₂, orFeI₂, a Cr halide such as CrCl₃, CrBr₃, or CrI₃, a Zr halide such asZrCl₄, ZrBr₄, or ZrI₄, a Mn halide such as MnCl₂, MnBr₂, or MnI₂, a Tihalide such as TiCl₃, TiBr₃, or TiI₃, a Ce halide such as CeCl₃, CeBr₃,or CeI₃, a Gd halide such as GdCl₃, GdBr₃, or GdI₃, or a combinationthereof. The first additive may be used alone or as a mixture of two ormore compounds.

The second additive may include sulfur-trioctylphosphine (S-TOP),sulfur-tributylphosphine (S-TBP), sulfur-triphenylphosphine (S-TPP),sulfur-trioctylamine (S-TOA), sulfur-octadecene (S-ODE),sulfur-diphenylphosphine (S-DPP), sulfur-oleylamine (S-oleylamine),sulfur-dodecylamine (S-dodecylamine), dodecanethiol (DDT), octanethiol,selenium-trioctylphosphine (Se-TOP), selenium-tributylphosphine(Se-TBP), selenium-triphenylphosphine (Se-TPP), selenium-octadecene(Se-ODE), selenium-diphenylphosphine (Se-DPP), selenium-dodecylamine(Se-Dodecylamine), tellurium-tributylphosphine (Te-TBP),tellurium-triphenylphosphine (Te-TPP), tellurium-trioctylphosphine(Te-TOP), tellurium-octadecene (Te-ODE), tellurium-diphenylphosphine(Te-DPP), tellurium-oleylamine (Te-Oleylamine), tellurium-dodecylamine(Te-dodecylamine), or a combination thereof.

The solvent may include a C6 to C22 primary alkylamine, a C6 to C22secondary alkylamine, a C6 to C40 tertiary alkylamine, anitrogen-containing heterocyclic compound, a C6 to C40 olefin, a C6 toC40 aliphatic hydrocarbon, an aromatic hydrocarbon substituted with a C6to C30 alkyl group, a phosphine substituted with a C6 to C22 alkylgroup, a phosphine oxide substituted with a C6 to C22 alkyl group, a C12to C22 aromatic ether, or a combination thereof. The solvent may beselected considering the precursors and organic ligands. The solvent mayinclude hexadecylamine, dioctylamine, trioctylamine, pyridine,octadecene, hexadecane, octadecane, squalane, phenyldodecane,phenyltetradecane, phenyl hexadecane, trioctylphosphine,trioctylphosphine oxide, phenyl ether, benzyl ether, or a combinationthereof, but it is not limited thereto.

The reaction may be performed under any suitable conditions by modifyinga temperature or a time, without a particular limit. For example, thereaction may be performed at a temperature of greater than or equal toabout 50° C., for example, a temperature of about 100° C. to about 240°C., for greater than or equal to about 1 second, for example, about 10seconds to about 20 minutes), but it is not limited thereto. Thereaction may be performed in an inert gas atmosphere, in an oxygenatmosphere, or in a vacuum, but it is not limited thereto.

In the device of some embodiments, the photoconversion layer may includea polymer matrix and the first quantum dot and the second quantum dotmay be dispersed in the polymer matrix. FIG. 4 shows a cross-sectionalview of the photoconversion layer in some non-limiting embodiments. Asshown in FIG. 4, the first quantum dot 10 and the second quantum dot 20are dispersed in the polymer matrix 30.

The polymer matrix may be a thiol-ene polymer, a (meth)acrylate-basedpolymer, a urethane-based resin, an epoxy-based polymer, a vinyl-basedpolymer, a silicone resin, or a combination thereof. The thiol-enepolymer is disclosed in US-2012-0001217-A1, which is incorporated hereinby reference in its entirety. The (meth)acrylate-based polymer such aspoly(methyl methacrylate (PMMA), the urethane-based resin such as anurethane acrylate, the epoxy-based polymer, the vinyl-based polymer suchas styrene, and the silicone resin such as polydimethylsiloxane (PDMS)may be synthesized by known methods, or may be commercially available.

An amount of the first and second quantum dot in the polymer matrix maybe appropriately selected and is not particularly limited. For example,the total combined amount of the first and second quantum dot in thepolymer matrix may be greater than or equal to about 0.1 weight percent(wt %), for example, greater than or equal to about 1 wt %, greater thanor equal to about 3 wt %, greater than or equal to about 5 wt %, greaterthan or equal to about 7 wt %, greater than or equal to about 10 wt %and less than or equal to about 60 wt %, for example, less than or equalto about 55 wt %, less than or equal to about 50 wt %, less than orequal to about 45 wt %, less than or equal to about 40 wt %, less thanor equal to about 35 wt %, or less than or equal to about 30 wt %, basedon the total weight of the quantum dot polymer composite, e.g., thephotoconversion layer, but is not limited thereto. A ratio between theamount of the first quantum dot and the amount of the second quantum dotis not particularly limited and may be appropriately selected in lightof a desired emission spectrum of the resulting photoconversion layer.In some embodiments, the first/second quantum dots may be mixed (e.g.,randomly dispersed) in the polymer matrix. In other embodiments, thephotoconversion layer may be patterned to have at least two differentsections and the first and the second quantum dots may be disposed indifferent sections, respectively.

A method of manufacturing a quantum dot polymer composite (e.g., as thephotoconversion layer) may include mixing a dispersion including thequantum dot with a solution including a polymer or a polymer precursor(e.g., a monomer), removing a solvent therefrom, and optionallyconducting a polymerization reaction or a curing process, but is notlimited thereto. The quantum dot-polymer composite thus obtained may bein a form of a quantum dot sheet (QD sheet).

The quantum dot polymer composite (e.g., the photoconversion layer) maybe patterned to have a first color section including the first quantumdot and a second color section including the second quantum dot. Methodsof patterning are not particularly limited. For example, a solutionincluding quantum dots and a polymer may be patterned via an ink-jetmethod or a screen printing method to form a patterned quantum dotpolymer composite, but the method is not limited thereto. Alternatively,a method using a photoresist may be used to form a desired pattern.

The photoconversion layer may show enhanced luminous properties. Forexample, BT2020 is a reference standard for color reproduction withrespect to a next generation display. The BT2020 has a significantlybroader color gamut as compared to the conventional reference standardssuch as NTSC, Adobe, DCI, or sRGB (see FIG. 11). In the electronicdevice of some embodiments, the light emitted from the photoconversionlayer may have a color gamut ratio that is greater than or equal toabout 87% with respect to BT2020 in the CIE1931 color space. The lightemitted from the photoconversion layer may a color gamut ratio that isgreater than or equal to about 88% with respect to BT2020 in the CIE1931color space. The light emitted from the photoconversion layer may acolor gamut ratio that is greater than or equal to about 90% withrespect to BT2020 in the CIE1931 color space. The color coordinate Cy ofthe green light among the light emitted from the photoconversion layermay be greater than or equal to about 0.73.

Hereinafter, a structure of an electronic device in some embodimentswill be explained in further detail, with reference to FIGS. 5 through10.

The electronic device may have a light source 110 having a peak emissionwavelength of about 440 nm to about 480 nm and a photoconversion layer130 capable of converting the light emitted from the light source intowhite light. Details of the photoconversion layer are the same as setforth above. The light source may include an LED light source. Dependingon the final structure of the device, the light source may constitute abacklight unit. In some other embodiments, the light source and thephotoconversion layer may form a backlight unit.

In some embodiments, the backlight unit may be an edge-type backlightunit. In an embodiment, for example, the backlight unit may include areflector (not shown), a light guide panel (not shown) disposed on thereflector in order to guide the light from the light source to theliquid crystal panel 200, and/or one or more optical sheets (not shown)such as a diffusion plate, a prism sheet, or the like, disposed on thelight guide, but is not limited thereto. In an alternative embodiment,the backlight unit may be a direct lighting type of backlight unit. Forexample, the backlight unit may have a reflector (not shown) and aplurality of fluorescent lamps disposed on the reflector with apredetermined (e.g., constant) interval therebetween; or may have alight emitting diode (“LED”)-driving substrate including a plurality ofLEDs, and may further include a diffusion plate, and optionally one ormore optical sheets on the diffusion plate.

Referring to FIG. 5 and FIG. 7, a light guide panel 120 may be disposedbetween the light source 110 and the photoconversion layer 130 orbetween the light source 110 and the liquid crystal panel 200. The lightguide panel may direct the light emitted from the light source 110toward the photoconversion layer 130 or toward the liquid crystal panel200. In such case, the light source 110 may include a plurality of LEDchips emitting light of a desired wavelength, for example, a wavelengthof about 440 nm to about 480 nm. For example, the light source 110 mayinclude an LED light source emitting blue light. A reflector (not shown)may be disposed under the lower surface of the light guide panel 120. InFIG. 5, the photoconversion layer 130 may be located and spaced at apredetermined distance from the light source 110, converting the lightemitted from the light source into white light. The backlight unit mayhave a structure which includes a light guide and an optical sheet, areflector, or the like, but is not limited thereto.

The backlight unit 100 may further include a diffusion plate (not shown)over the light guide panel 120. The photoconversion layer 130 may bedisposed either between the light guide panel 120 and the diffusionplate or over the diffusion plate (e.g., over a surface opposite to thesurface facing the light guide panel 120). The light emitted from thelight source 110 may pass through the photoconversion layer 130 toproduce white light in which blue light, green light, and red light aremixed. In this case, changing the composition, the size, and the weightratio of the first quantum dot and the second quantum dot may allow forcontrol over the mixing of the blue light, the green light and the redlight at a desired ratio, thereby making it possible to obtain whitelight having an improved color gamut ratio and an increased colorpurity. Alternatively, as shown in FIG. 7 and the like, the light source110 emits blue light, which is directed into the liquid crystal panel.

The electronic device may further include a liquid crystal panel 200 andthe light emitted from the backlight unit 100 may enter the liquidcrystal panel 200, pass through one or more color filter to form animage having a desired color on a screen. The color filter may be anabsorption type or photoluminescent type color filter.

The liquid crystal panel 200 may include a lower substrate 210, an uppersubstrate 240 disposed opposite to the lower substrate, and a liquidcrystal layer 220 interposed between the upper and lower substrates.

Referring to FIG. 5 and FIG. 6, the liquid crystal panel may include anabsorption type color filter 230, the photoconversion layer may emitwhite light, and the liquid crystal panel may be disposed on thephotoconversion layer a manner such that the white light passes throughthe liquid crystal layer.

An optical element 300 may be disposed above and/or below the liquidcrystal panel 200. The optical element 300 may include a polarizer, andmay be a polarizing plate.

The lower substrate 210, also referred to be as an array substrate, mayinclude a transparent insulation material substrate. The transparentinsulation material substrate may include a glass substrate, a polymersubstrate including a polyester such as polyethylene terephthalate(“PET”) or polyethylene naphthalate (“PEN”), a polycarbonate, apolyacrylate, a polysiloxane, or a combination thereof, or an inorganicmaterial substrate such as, Al₂O₃, ZnO, and the like).

A wire plate 211 may be disposed on an internal surface, e.g., a topsurface, of the lower substrate 210. The wire plate 211 may include aplurality of gate wires (not shown) and data wires (not shown), a thinfilm transistor (not shown) disposed adjacent to a crossing region ofgate wires and data wires, and a pixel electrode (not shown) for eachpixel area, but is not limited thereto. In one embodiment, for example,pixel areas may be defined by the gate and data wires. The wire plate211 may have any suitable structure or feature, and is not particularlylimited.

The liquid crystal layer 220 may be disposed on the wire plate 211. Theliquid crystal layer 220 may include an alignment layer 221 on oppositesurfaces thereof for initial alignment of the liquid crystal materialincluded in the liquid crystal layer 220. The liquid crystal materialand the alignment layer 221 may have any appropriate structure orfeature and details thereof, such as the composition of the liquidcrystal material, the composition of the alignment layer material, amethod of forming the liquid crystal layer, and a thickness of theliquid crystal layer, are not particularly limited.

The optical element 300 (polarizing plate) may be disposed on anexternal surface of the lower substrate 210, e.g., under the lowersubstrate 210. Materials and structures of the polarizing plate 300 arenot particularly limited. The backlight unit 100 that emits blue lightmay be disposed under the polarizing plate 300.

The upper substrate 240 (also referred to as a color filter substrate)may be a transparent insulation material substrate. The transparentinsulation material substrate may include a glass substrate, a polymersubstrate including a polyester such as PET and PEN, a polycarbonate, apolyacrylate, a polysiloxane, or a combination thereof, or an inorganicmaterial substrate such as Al₂O₃, ZnO, and the like). The opticalelement 300 may be disposed on a surface (e.g. a top surface) of theupper substrate 240. The optical element 300 on the surface of the uppersubstrate may be included for maintaining polarization of light emittedfrom the color filter layer. In some embodiments, for example, theoptical element 300 may be a polarizer. The polarizer may includetriacetyl cellulose (“TAC”), having a thin thickness of less than orequal to about 200 micrometers (μm), but is not limited thereto. In analternative embodiment, the optical element 300 may be a refractiveindex-controlling coating without a polarization function.

A black matrix 241 having an opening defined therethrough may bedisposed on the upper substrate 240, e.g., the bottom or the top surfaceof the upper substrate 240, and may be positioned so as to cover a gateline, a data line, a thin film transistor, or the like, of the wireplate 211 disposed on the lower substrate 210. In one exemplaryembodiment, for example, the black matrix 241 may have a lattice shape.

An absorption type color filter layer 230 including a first colorsection (a red color filter, R) configured for passing red light, asecond color section (a green color filter, G) configured for passinggreen light, and a third color section (a blue color filter, B)configured for passing blue light may be disposed over the black matrix241 (e.g., in the openings of the lattice structure of the black matrix241).

In some embodiments, the green filter (G) of the absorption type colorfilter may have a normalized transmission ratio of less than or equal toabout 0.2, for example, less than or equal to about 0.1, or for example,zero (0), with respect to light of a wavelength of 500 nm or lower, forexample, with respect to light of a wavelength of 480 nm or lower. Theblue filter (B) of the absorption type color filter may have anormalized transmission ratio of less than or equal to about 0.2, forexample, less than or equal to about 0.1, or for example, zero (0), withrespect to light of a wavelength of 520 nm or higher.

As used herein, the normalized transmission ratio is calculated based onthe maximum transmission thereof, which is assumed to be one (1). Thespectrum of the light that is emitted from the photoconversion layer andpasses through the second color section (G) may not include an emissionpeak having an intensity of greater than about 0.096, for example, forexample, greater than about 0.1 at a wavelength of less than about 500nm. The spectrum of the light that is emitted from the photoconversionlayer and passes through the third color section (B) may not include anemission peak having an intensity of greater than about 0.13, forexample, greater than 0.15 at a wavelength of greater than about 500 nm.When the absorption color filter having the foregoing properties isused, the display device may realize a greater color gamut and may havean enhanced color gamut ratio under the BT2020 standard. As used herein,the normalized intensity is a peak intensity that is calculated based onthe maximum peak intensity, which is assumed to be one (1).

The first color section, the second color section, and the third colorsection of the absorption type color filter 230 may be repeated on theupper substrate 240 to correspond to the pixel regions defined in thewire plate 211.

In other embodiments, the liquid crystal panel 200 included in theelectronic device does not include an absorption type color filter andthe photoconversion layer 130 is patterned in such a manner that it mayact as a photoluminescent color filter layer when disposed on the top orbottom surface of the upper substrate 240 of the liquid crystal panel. Atransparent common electrode 131 may be disposed on the photoconversionlayer 130 (e.g., photoluminescent color filter layer). (See for example,FIG. 6)

For example, the photoluminescent color filter layer (e.g., thephotoconversion layer 130) may include a pattern having a first colorsection (R) emitting red light having a peak emission wavelength (e.g.,a maximum peak emission wavelength) of about 620 nm to about 650 nm, asecond color section (G) emitting green light having a peak emissionwavelength (e.g., a maximum peak emission wavelength) of about 500 nm toabout 550 nm. The pattern may further include a third color section (B)emitting blue light having a peak emission wavelength (e.g., a maximumpeak emission wavelength) of about 440 nm to about 480 nm. If desired,the photoluminescent color filter layer may further include a fourthcolor section (e.g., a fourth color filter) for emitting other colorswhich are different from the colors of the red, green and blue light,for example, colors such as cyan, magenta, and yellow. Thephotoluminescent color filter layer may include a quantum dot pattern ora quantum dot polymer composite pattern. The quantum dot pattern and thequantum dot polymer composite pattern may be formed using the methoddisclosed in U.S. Pat. No. 7,199,393, which is incorporated herein byreference in its entirety, but the method is not limited thereto. Thequantum dot polymer composite pattern may be formed, for example, via apatterning process involving a use of a photoresist that includespreparing a quantum dot containing photosensitive composition, forming athin film, exposing the film, and developing the exposed film. However,the patterning process is not limited thereto.

In some embodiments, a pattern for the photoluminescent color filterlayer may be formed in the manner schematically illustrated in FIG. 37,and described below.

For example, the patterning may be carried out in the following manner:

[1] A toluene dispersion of quantum dots (e.g., InP/ZnS including anorganic ligand such as oleic acid bound to a surface thereof) emittingred light is prepared. The toluene dispersion including 50 grams (g) ofthe quantum dot is mixed with 100 g of a binder solution to provide aquantum dot-binder dispersion. The binder solution may include a fourmembered copolymer of methacrylic acid, benzyl methacrylate,hydroxyethyl methacrylate, and styrene (acid value: 130 milligrams (mg)per gram of KOH (mg KOH/g), a weight average molecular weight: 8,000, amolar ratio of acrylic acid:benzyl methacrylate:hydroxyethylmethacrylate:styrene=61.5%:12%:16.3%:10.2%) in a solvent (polypropyleneglycol monomethyl ether acetate having a concentration of 30 percent byweight, wt %).

To the prepared quantum dot-binder dispersion, the following may beadded to obtain a photosensitive composition: glycoldi-3-mercaptopropionate, hexaacrylate having the structure below (as aphotopolymerizable monomer), 1 g of an oxime ester compound (as aninitiator), TiO₂ (as a light diffusing agent), and propylene glycolmonomethyl ether acetate (PGMEA) (as a solvent).

wherein,

The photosensitive composition thus obtained is spin-coated on a glasssubstrate to provide a film (S100). The obtained film is pre-baked at100° C. (S200). The pre-baked film is irradiated with light (wavelength:365 nanometers (nm), intensity: 60 millijoules, mJ) for 1 s under a maskhaving a predetermined pattern (S300) and developed by a potassiumhydroxide-diluted aqueous solution (concentration: 0.043%) to provide apattern (S400). The obtained pattern is subjected to 30 min of heatingat 180° C. to obtain a pattern of red (R) quantum dot polymer composite(S500).

[2] A pattern of green (G) quantum dot polymer composite is prepared inthe same manner of item [1] except for using a toluene dispersion of aperovskite quantum dot emitting green light.

[3] A pattern of polymer composite (B) is prepared in the same manner asset forth in item [1] except the quantum dot is not used.

Referring FIG. 7, the electronic device of some embodiments (e.g., thephotoluminescent liquid crystal display) may include a liquid crystalpanel 200, an optical element 300 (e.g., a polarizing plate) disposedabove and below the liquid crystal panel 200, and a backlight unitincluding a light source 110 emitting blue light and disposed under thelower optical element 300. The liquid crystal panel 200 includes a lowersubstrate 210, an upper substrate 240, a liquid crystal layer 220interposed between the upper and lower substrates, and a photoconversionlayer 130 disposed on the bottom surface of the upper substrate 240 as aphotoluminescent color filter layer.

In other embodiments, referring to FIG. 8, the liquid crystal panel 200includes a lower substrate 210, an upper substrate 240, a liquid crystallayer 220 interposed between the upper and lower substrates, and aphotoconversion layer 130 disposed on the top surface of the uppersubstrate 240 as a photoluminescent color filter layer.

In some embodiments, the electronic device may further include a bluelight blocking layer 250 (or blue filter BF). The blue light blockinglayer may be disposed between the bottom surface of the first colorfilter (R) and the second color filter (G) and the upper substrate 240(see FIG. 9). Alternatively, the blue light blocking layer 250 may bedisposed on the optical element 300 (see FIG. 10). In an embodiment, theblue light blocking layer 250 may be a sheet having an opening in aregion corresponding to a pixel area (third color filter) expressingblue. In such an embodiment, the blue light blocking layer 250 may bedisposed on a region corresponding to the first and second colorfilters. In one embodiment, for example, the blue light blocking layer250 may be formed by alternately stacking at least two layers havingdifferent refractive indexes, and the blue light blocking layer 250transmits light wavelengths other than the blue wavelength band andblocks the blue wavelength band. The blocked light of blue wavelengthmay be reflected and recycled. The blue light blocking layer 250 mayprevent light emitted from the blue light source 110 of the backlightunit from being directly emitted to the outside.

The electronic device of the embodiments may show improved brightness,for example, a brightness which is two to three times higher than thatof an electronic device using a conventional white light source, we wellas improved display quality (e.g., improved color reproducibility).

Hereinafter, the embodiments are illustrated in more detail withreference to examples. However, they are example embodiments of thepresent invention, and the present invention is not limited thereto.

EXAMPLES Analysis [1] Photoluminescence Analysis

A Hitachi F-7000 spectrometer is used to perform a photoluminescencespectrum analysis by irradiating light having a wavelength of 458 nm.Based on the obtained photoluminescence spectrum, a maximumphotoluminescence peak wavelength, quantum efficiency, and a full widthat half maximum (FWHM) are calculated.

[2] TEM Analysis

A transmission electron microscope image is obtained by using aTEM-TITAN-80-300 (FEI) equipment at an acceleration voltage of 300 KV.From the TEM analysis results, an average diameter of a quantum dot maybe measured.

[3] X-ray Diffraction Analysis

An X-ray diffraction spectrum is obtained using a Philips XPert PROequipment.

[4] EDX Analysis

An EDS measuring device mounted on the TEM-TITAN-80-300 (FEI) is used toperform an energy-dispersing X-ray spectrum analysis.

[5] XPS Analysis

Quantum 2000 made by Physical Electronics, Inc. is used to perform anXPS element analysis under a condition of an acceleration voltage:0.5-15 kiloelectron volts (keV), 300 watts (W), and a minimum analysisarea: 200×200 square micrometer (μm²).

[6] ICP Analysis

ICPS-8100 (Shimadzu Corp.) is used to perform an inductively-coupledplasma-element releasing spectrum analysis.

Synthesis of First Quantum Dot: Reference Example 1: Preparation ofGreen Quantum Dot

(1) 0.2 millimole (mmol) of indium acetate, 0.6 mmol of palmitic acid,and 10 milliliters (mL) of 1-octadecene are placed in a flask, subjectedto a vacuum state at 120° C. for one hour, and then heated to 280° C.after the atmosphere in the flask is exchanged with N₂. Then, a mixedsolution of 0.1 mmol of tris(trimethylsilyl)phosphine (TMS3P) and 0.5 mLof trioctylphosphine (TOP) is quickly injected and the reaction proceedsfor 20 minutes. The reaction mixture is rapidly cooled to roomtemperature and acetone is added thereto to precipitate nanocrystals,which are then separated by centrifugation and dispersed in toluene. Thefirst absorption maximum in UV-VIS spectrum of the InP core nanocrystalsthus prepared is in the range of 420-600 nm.

0.3 mmol (0.056 g) of zinc acetate, 0.6 mmol (0.189 g) of oleic acid,and 10 mL of trioctylamine are placed in a flask, subjected to a vacuumstate at 120° C. for 10 minutes, and then heated to 220° C. after theatmosphere in the flask is exchanged with N₂. Then, a toluene dispersionof the prepared InP core nanocrystals (optical density: 0.15) and 0.6mmol sulfur trioctylphosphine (S-TOP) are added to the flask and thenthe resulting mixture is heated to 280° C., and the reaction proceedsfor 30 minutes. After the reaction, the reaction solution is quicklycooled to room temperature to obtain a reaction mixture includingInP/ZnS semiconductor nanocrystals.

(2) An excess amount of ethanol is added to the reaction mixtureincluding the InP/ZnS semiconductor nanocrystals, which is thencentrifuged to remove an extra organic material in the reaction mixtureof the semiconductor nanocrystals. After centrifugation, the supernatantis discarded and the precipitate is dispersed in hexane again, and anexcess amount of ethanol is added thereto and the resulting mixture iscentrifuged again. The precipitate obtained from the centrifugation isdried and dispersed in chloroform. A UV-vis absorption wavelength of theresulting quantum dot is about 498 nm, its maximum peak emissionwavelength is about 520 nm, its quantum yield thereof is about 90%, andits FWHM is about 38 nm.

Reference Example 2: Preparation of Red Quantum Dot

A quantum dot emitting red light is prepared in the same manner exceptfor varying a ratio between the precursors. A UV-vis absorptionwavelength of the resulting quantum dot is about 625 nm, its maximumpeak emission wavelength is about 645 nm, its quantum yield thereof isabout 95%, and its FWHM is about 40 nm.

Synthesis of Second Quantum Dot: Reference Example 3: Synthesis ofPerovskite Green Quantum Dot Having a Composition of CsPbBr_(3+α) Dopedwith Zn and Se

[1] Preparation of Cs Precursor Solution

Cs₂CO₃ (0.8 grams (g), Sigma-Aldrich, 99%) is put into a 100 milliliter(mL) 3-neck flask along with octadecene (30 mL, Sigma-Aldrich, 90%, ODE)and oleic acid (2.5 mL, Sigma-Aldrich, 90%, OA), and the mixture isdried at 120° C. for one hour, and subsequently heated at 150° C. underN₂ to react the Cs₂CO₃ with the oleic acid and thereby obtain a firstprecursor of Cs-oleate. The Cs-oleate is precipitated from the ODE atroom temperature and heated up to 100° C. before being injected into thereaction solution.

[2] Preparation of a Solution Containing a Second Precursor and a FirstAdditive

The ODE (50 mL), PbBr₂ (0.69 g, Sigma-Aldrich Co., Ltd., 99.999%), andZnBr₂ (0.42 g, Sigma-Aldrich Co., Ltd., 99.999%) are placed in a 250 mL3-neck flask and dried at 120° C. for one hour. Then, dry oleylamine (5mL, STREM Chemicals, 95%, OLA) and dry OA (5 mL) are injected thereintoat 120° C. under a nitrogen atmosphere, and the obtained mixture isstirred to dissolve the PbBr₂ and the ZnBr₂ to prepare a solutioncontaining a second precursor and a first additive.

[3] The obtained solution containing the second precursor and the firstadditive is heated at a temperature of 200° C., the first precursorsolution obtained from [1] is rapidly injected thereto, and then Se-TOP(1.6 mmol) is added thereto. The Se-TOP is prepared as a 0.4 molar (M)solution by dissolving Se powder (RND Korea Co., LTD., 99.999%) inTri-n-octylphosphine (STREM Chemicals, 97%, TOP). After five minutes,the reaction solution is rapidly cooled to room temperature.

[4] Subsequently, as a non-solvent, isopropanol is added to the cooledreaction solution to form a precipitate, which is then washed. Theprecipitate is centrifuged to obtain a quantum dot, and the obtainedquantum dot is dispersed in toluene and lauryl methacrylate,respectively. A Transmission Electron Microscopic (TEM) analysis iscarried out for the obtained quantum dots. The results of the TEManalysis confirm that the obtained quantum dots have a cubic orrectangular cuboid shape and their average size is about 10 nm.

For the obtained quantum dots, an X-ray diffraction (XRD) analysis iscarried out. The results of the XRD analysis confirm that the preparedquantum dots include a compound having a perovskite structure.

For the obtained quantum dots, a photoluminescence analysis is carriedout. A UV-vis absorption wavelength of the resulting quantum dot isabout 520 nm, its maximum peak emission wavelength is about 525 nm, itsquantum yield thereof is about 95%, and its FWHM is about 22 nm.

The toluene dispersion including the quantum dots is kept in the air. Aphotoluminescence spectrum analysis of the quantum dots for thedispersion is performed both after 24 hours and after 48 hours and theresults are summarized in Table 1.

Reference Example 4: Synthesis of Perovskite Green Quantum Dot Having aComposition of Se-Doped CsPbBr_(3+α)

A quantum dot doped with Se and including CsPbBr_(3+α) is prepared inthe same method as Reference Example 3, except for not using ZnBr₂ as afirst additive, and a toluene dispersion including the prepared quantumdots are obtained. The obtained quantum dots have a cubic or rectangularcuboid shape and their average size is about 10 nm.

Reference Example 5: Synthesis of Perovskite Green Quantum Dot Having aComposition of Zn-Doped CsPbBr_(3+α)

A quantum dot doped with Zn and including CsPbBr_(3+α) is prepared inthe same method as Reference Example 1 except for not using the Se-TOPas a second additive, and the toluene dispersion each including theprepared quantum dots is obtained. The obtained quantum dots have acubic or rectangular cuboid shape and their average size is about 10 nm.

The toluene dispersion is kept in the air. A photoluminescence spectrumanalysis of the quantum dot for each of the dispersions is performedafter 24 hours and after 48 hours, and the results are summarized inTable 1.

TABLE 1 After dispersion Toluene dispersion Toluene dispersion intoluene after 24 h after 48 h λ FWHM λ FWHM λ FWHM Sample (nm)^(a) (nm)QE (nm) (nm) QE (nm) (nm) QE Reference 506 23 93 508 22 103 507 22 100Example 3 Reference 508 23 78 507 23 85 507 23 93 Example 5

The results of Table 1 confirm that even when the quantum dots thussynthesized are washed with isopropanol and dispersed in toluene, theymay maintain a relatively narrow FWHM and a suitable improvement inquantum efficiency (QE).

Reference Example 6: Synthesis of a Perovskite Quantum Dot Emitting RedLight and Having a Composition of Zn and Se-Doped CsPbI_(3+α)

A perovskite quantum dot emitting red light is prepared in the samemethod as Reference Example 3, except for using PbI₂ and ZnI₂ instead ofPbBr₂ and ZnBr₂. For the obtained quantum dots, a photoluminescenceanalysis is carried out. A UV-vis absorption wavelength of the resultingquantum dot is about 622 nm, its maximum peak emission wavelength isabout 645 nm, its quantum yield thereof is about 90%, and its FWHM isabout 46 nm.

Experimental Example 1: Element Analysis of Perovskite Quantum Dot [1]TEM-EDX Analysis

For the quantum dots prepared in Reference Example 3, a TEM-EDX-analysisis carried out. As a result, in case of the quantum dot of ReferenceExample 3, an atomic ratio of the Br with respect to the Cs is 3.14. Theaforementioned results confirm that the quantum dots of ReferenceExample 3 include an excess amount of halogen.

[2] XPS Analysis

For the quantum dots prepared in Reference Example 3, an XPS analysis iscarried out. The results confirm that in case of the quantum dots ofReference Example 3, the atomic ratio of the Br with respect to Pb(Pb4f/Br3d) is 66.0%/22.6%. The results also confirm that the quantumdots of Reference Example 3 include an excess amount of the Br.

[3] ICP-AES Analysis

For the quantum dots of Reference Example 3, an ICP-AES analysis iscarried out, and the results are shown below in Table 2:

TABLE 2 Mole ratio ppm Samples Zn Pb Se Zn Pb Se Reference 0.115 0.80.085 0.04 0.95 0.04 Example 3

The results confirm that the quantum dots of Reference Example 3 includeZn and Se.

Preparation of Photoconversion Layer, Production of Device, and Analysisof Luminous Properties Thereof Comparative Example 1 [1] Preparation ofPhotoconversion Layer

30 wt % of lauryl methacrylate, 36 wt % of tricyclodecane dimethanoldiacrylate, 4 wt % of trimethylol propane triacrylate, 20 wt % of epoxydiacrylate oligomer (Manufacturer: Sartomer), 1 wt % of1-hydroxy-cyclohexyl-phenyl-ketone, and 1 wt % of2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide are mixed to prepare amonomer and oligomer mixture. The mixture is de-foamed under vacuum.

The green quantum dot synthesized in Reference Example 1 and the redquantum dot synthesized in Reference Example 2 are mixed with an excessamount of ethanol again and centrifuged. A mixing ratio between thegreen quantum dot and the red quantum dot is about 5:4 as calculatedfrom the volume of the dispersion and the optical density thereof. Theseparated quantum dots are dispersed in 0.15 g (10 wt % of the entirecomposition except for an initiator) of lauryl methacrylate, and thenadded to 1.35 g of the mixture prepared above, and vortexed to prepare aquantum dot composition.

About 1 g of the quantum dot composition thus prepared is drop-cast on asurface of a PET film sputtered with SiOx (purchased from I-component,hereinafter, a barrier film). Another barrier film is placed on thecasted composition and a UV-curing (exposure to ultraviolet (UV) light)is carried out for 10 seconds (photo intensity: 100 milliwatts persquare centimeter (mW/cm²)) to provide a photoconversion layer.

[2] Production of Electronic Device

The photoconversion layer obtained in [1] is inserted between a lightguide panel and an optical sheet of a 60-inch TV mounted with a blue LEDhaving a peak emission wavelength of 449 nm, and then color filter 1(manufactured from Samsung Display Co., Ltd.) is disposed on the opticalsheet. The resulting TV is operated and luminance properties thereof aremeasured at a distance of about 45 centimeters (cm) withspectroradiometer (Konica Minolta Inc., CS-2000) to obtain a colorcoordinate value (Cx, Cy) and a color gamut.

The results are summarized in Table 3, Table 4, FIG. 12, FIG. 14, andFIG. 15.

Example 1

[1] Preparation of Photoconversion Layer

A monomer and oligomer mixture is prepared in the same manner asComparative Example 1. The mixture thus prepared is de-foamed undervacuum.

A photoconversion layer is prepared in the same manner as set forth inComparative Example 1 except for using the toluene dispersion of the redquantum dot synthesized in Reference Example 2 and the toluenedispersion of the green quantum dot synthesized in Reference Example 3as red and green quantum dots.

[2] Production of Electronic Device

The photoconversion layer obtained in [1] is inserted between a lightguide panel and an optical sheet of a 60-inch TV mounted with a blue LEDhaving a peak emission wavelength of 449 nm, and then a color filter(manufactured from Samsung Display Co., Ltd.) is disposed on the opticalsheet. The resulting TV is operated and luminance properties thereof aremeasured at a distance of about 45 cm with a spectro-radiometer (KonicaMinolta Inc., CS-2000) to obtain a color coordinate value (Cx, Cy) and acolor gamut.

The results are summarized in Table 3, Table 4, FIG. 13, FIG. 14, FIG.15, and FIG. 16.

The RGB spectrums of the light emitted from the device are shown in FIG.17 to FIG. 19.

For color filter 1, the red light transmittance with respect to thewavelengths of the red (R) section, the green light transmittance withrespect to the wavelengths of the green (G) section, and the blue lighttransmittance with respect to the wavelengths of the blue (G) section,are shown in FIGS. 23 to 25, respectively.

Comparative Example 2

A device is produced in the same manner set forth in Example 1 exceptfor using color filter 2 instead of color filter 1 (prepared fromSamsung Display Co., Ltd.). The resulting TV is operated and luminanceproperties thereof are measured at a distance of about 45 cm withspectro-radiometer (Konica Minolta Inc., CS-2000) to obtain a colorcoordinate value (Cx, Cy) and a color gamut.

The results are summarized in Table 3, Table 4, and FIG. 16.

The RGB spectrums of the light emitted from the device are shown in FIG.20 to FIG. 22.

For color filter 2, the red light transmittance with respect to thewavelengths of the red (R) section, the green light transmittance withrespect to the wavelengths of the green (G) section, and the blue lighttransmittance with respect to the wavelengths of the blue (G) sectionare shown in FIGS. 23 to 25.

Comparative Example 3

A device is produced in the same manner set forth in Example 1 exceptfor using the green quantum dot synthesized in Reference Example 1 andthe red quantum dot synthesized in Reference Example 6 as red and greenquantum dots. The resulting TV is operated and luminance propertiesthereof are measured at a distance of about 45 cm withspectro-radiometer (Konica Minolta Inc., CS-2000) to obtain a colorcoordinate value (Cx, Cy) and a color gamut.

The results are summarized in Table 3, Table 4, FIG. 33, and FIG. 34.

TABLE 3 Color coordinate (Cy, Cx) Blue Red Green White Comp. (0.1488,0.0381) (0.6942, 0.3012) (0.1616, 0.7195) (0.2705, EX 1  0.2400) EX 1(0.1501, 0.0337) (0.6969, 0.2986) (0.1574, 0.7537) (0.2704,  0.2407)Comp. (0.1479, 0.0653) (0.6958, 0.2941) (0.1667, 0.6627) (0.2700, EX 2 0.2399) Comp. (0.1496, 0.0349) (0.6751, 0.3201) (0.1950, 0.7123)(0.2700, EX 3  0.2400)

TABLE 4 Color gamut ratio (%) with respect with respect with respectwith respect to to NTSC to Adobe to DCI BT2020 Comp. EX 1 94.1%  96.9%90.7% 85.8% EX 1 98.3% 100.0% 95.3% 90.2% Comp. EX 2 85.7%  89.1% 84.3%76.2% Comp. EX 3 96.6%  99.5% 94.6% 80.2%

The results of Table 3 and Table 4, and the results of FIG. 14 and FIG.15, confirm that the device of Example 1 having the photoconversionlayer including the first quantum dot and the second quantum dot mayexhibit significantly enhanced display quality in terms of the colorgamut ratio in comparison with the devices of Comparative Example 1 andComparative Example 3.

The results of FIGS. 24 to 25 confirm that in the color filter used inExample 1, the green (G) section has a normalized transmission of aboutzero with respect to light of a wavelength of less than or equal toabout 475 nm and the blue (B) section has a normalized transmission ofabout zero with respect to light of a wavelength of greater than orequal to about 530 nm. The results of FIGS. 23 to 25 confirm that in thecolor filter used in Comparative Example 2, the green (G) section has anormalized transmission of about 0.4 with respect to light of awavelength of less than or equal to about 475 nm and the blue (B)section has a normalized transmission of about 0.4 with respect to lightof a wavelength of greater than or equal to about 510 nm.

The results of Table 3 and Table 4 and the results of FIG. 16 confirmthat the device of Example 1 having the photoconversion layer of thefirst quantum dot and the second quantum dot may exhibit significantlyenhanced display quality in terms of the color gamut ratio in comparisonwith the device of Comparative Example 2.

The RGB spectrums of FIGS. 17 to 19 confirm that when the light isemitted from the photoconversion layer of the device of Example 1 andpasses through the second color section, the spectrum does not includean emission peak having an normalized intensity of greater than about0.07 at a wavelength of less than about 500 nm and when the light isemitted from the photoconversion layer of the device of Example 1 andpasses through the third color section, the spectrum does not include anemission peak having an normalized intensity of greater than about 0.05at a wavelength of greater than about 500 nm.

The RGB spectrums of FIGS. 20 to 22 confirm that when the light isemitted from the photoconversion layer of the device of ComparativeExample 2 and passes through the second color section, the spectrumincludes an emission peak having an normalized intensity of greater thanabout 0.095 at a wavelength of less than about 500 nm and when the lightis emitted from the photoconversion layer of the device of ComparativeExample 2 and passes through the third color section, the spectrumincludes an emission peak having an normalized intensity of greater thanabout 0.128 at a wavelength of greater than about 500 nm.

Example 2

A pattern including the red quantum dot (R QD) synthesized in ReferenceExample 2, a pattern including the green perovskite quantum dot (G PQD)synthesized in Reference Example 3, a device including these patternsare simulated using an EXCEL program and based on the photoluminescentspectrums of the quantum dots measured by the spectrometer, the colorcoordinates (Cx, Cy) of the light emitted from the device arecalculated, and the results are summarized in Table 5, Table 6, FIG. 28,and FIG. 29.

Comparative Example 4

A pattern including the red quantum dot (R QD) synthesized in ReferenceExample 2, a pattern including the green quantum dot (G QD) synthesizedin Reference Example 1, a device including these patterns are simulatedusing an EXCEL program and based on the photoluminescent spectrums ofthe quantum dots measured by the spectrometer, the color coordinates(Cx, Cy) of the light emitted from the device are calculated and theresults are summarized in Table 5, Table 6, FIG. 28, and FIG. 29.

Comparative Example 5

A pattern including the red perovskite quantum dot (R PQD) synthesizedin Reference Example 6, a pattern including the green quantum dot (G QD)synthesized in Reference Example 1, a device including these patternsare simulated with using EXCEL program and based on the photoluminescentspectrums of the quantum dots measured by the spectrometer, the colorcoordinates (Cx, Cy) of the light emitted from the device are calculatedand the results are summarized in Table 5, Table 6, FIG. 28, and FIG.29.

TABLE 5 Color Coordinates (Cy, Cx) Blue Red Green White EX 2 (0.1519,0.0288) (0.6671, 0.3023) (0.1476, 0.7820) (0.2700,  0.2401) Comp.(0.1519, 0.0288) (0.6671, 0.3023) (0.1660, 0.7021) (0.2700, EX 4 0.2398) Comp. (0.1519, 0.0288) (0.6730, 0.3268) (0.1920, 0.7157)(0.2700, EX 5  0.2400)

TABLE 6 Color gamut ratio (%) with respect with respect with respectwith respect to NTSC to NTSC to NTSC to NTSC EX 2 96.9% 99.9% 93.9%88.5% Comp. EX 4 89.0% 92.9% 87.0% 79.4% Comp. EX 5 97.3% 99.5% 95.1%80.5%

The results of Table 5, Table 6, FIG. 28 and FIG. 29 confirm that theelectronic device of Example 2 may show further enhanced color gamutratio in comparison with those of the devices and Comparative Examples 4and 5.

While this disclosure has been described in connection with what ispresently considered to be practical example embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. An electronic device comprising: a layercomprising a perovskite quantum dot having a perovskite crystalstructure and the perovskite quantum dot comprises a compoundrepresented by Chemical Formula 1:AB′X_(3+α)  Chemical Formula 1 wherein A is a Group IA metal selectedfrom Rb, Cs, Fr, and a combination thereof, NR₄ ⁺, wherein each R isindependently a hydrogen atom or a substituted or unsubstituted C1 toC10 straight chain or branched chain alkyl group, [CH(NH₂)₂]⁺, or acombination thereof; B′ is a Group IVA metal selected from Si, Ge, Sn,Pb, and a combination thereof; X is a halogen selected from F, Cl, Br,I, and a combination thereof, BF₄ ⁻, or a combination thereof, and α is0 to 3, and wherein the perovskite quantum dot comprises a greateramount of halogen than a stoichiometric amount for a perovskite crystal,and wherein the device is configured to emit light having a color gamutratio of at least about 80% with respect to BT2020 in a CIE1931 colorspace.
 2. The electronic device of claim 1, wherein a mole ratio of theX to the A is greater than or equal to about 3.3.
 3. The electronicdevice of claim 2, wherein the mole ratio of the X to the A is measuredby transmission electron microscope-energy dispersive X-rayspectroscopy.
 4. The electronic device of claim 1, wherein a mole ratioof the X to the A is greater than or equal to about 3.4.
 5. Theelectronic device of claim 1, wherein a mole ratio of the X to the A isgreater than or equal to about 3.5.
 6. The electronic device of claim 1,wherein the electronic device further comprises a light source and thelayer is disposed on the light source.
 7. The electronic device of claim1, wherein the light source emits light having a peak emission at awavelength of about 440 nanometers to about 480 nanometers.
 8. Theelectronic device of claim 1, wherein the layer comprises a polymermatrix, and the first quantum dot and the second quantum dot aredispersed in the polymer matrix.
 9. The electronic device of claim 1,wherein a peak emission wavelength of the red light is of about 620nanometers to about 650 nanometers and a peak emission wavelength of thegreen light is of about 500 nanometers to about 550 nanometers.
 10. Theelectronic device of claim 1, wherein the layer comprises a firstquantum dot, which is configured to emit red light, and a second quantumdot, which is configured to emit green light, and at least one of thefirst quantum dot and the second quantum dot comprises the perovskitequantum dot.
 11. The electronic device of claim 10, wherein at least oneof the first quantum dot and the second quantum dot comprises anon-perovskite quantum dot not having a perovskite crystal structure andthe non-perovskite quantum dot comprises a Group II-VI compound, a GroupIII-V compound, a Group IV-VI compound, a Group IV element, a Group IVcompound, a Group I-III-VI compound, a Group I-II-IV-VI compound, or acombination thereof.
 12. The electronic device of claim 11, wherein thefirst quantum dot comprises the non-perovskite quantum dot and thesecond quantum dot comprises the perovskite quantum dot.
 13. Theelectronic device of claim 12, wherein the non-perovskite quantum dotcomprises a Group II-VI compound, a Group III-V compound, or acombination thereof.
 14. The electronic device of claim 10, wherein thelayer comprises a pattern having a first color section and a secondcolor section, and wherein the first color section comprises the firstquantum dot and the second color section comprise the second quantumdot.
 15. The electronic device of claim 1, wherein in Chemical Formula1, the A is the Group IA metal.
 16. The electronic device of claim 1,wherein the perovskite quantum dot further comprises at least one of afirst dopant and a second dopant, wherein the first dopant comprisespotassium or a first metal having a crystal ionic radius of less thanabout 133 picometers and which is different from the Group IVA metaland, if present, the Group IA metal, and the second dopant comprises anon-metal element which forms a bond with the Group IVA metal.
 17. Theelectronic device of claim 14, wherein the first metal comprises Zn, Hg,Ga, In, Tl, Cu, Al, Li, Na, Be, Mg, Ag, Pt, Pd, Ni, Co, Fe, Cr, Zr, Mn,Ti, Ce, Gd, or a combination thereof, and the non-metal elementcomprises S, Se, Te, or a combination thereof.
 18. The electronic deviceof claim 1, wherein the quantum dot comprises an organic ligand compoundon a surface thereof, wherein the organic ligand compound is selectedfrom RCOOH, RNH₂, R₂NH, R₃N, RSH, R₃PO, R₃P, ROH, RCOOR′, RPO(OH)₂,R₂POOH, and RCOOCOR′, wherein, R and R′ are independently a substitutedor unsubstituted C1 to C24 aliphatic hydrocarbon group or a substitutedor unsubstituted C5 to C24 aromatic hydrocarbon group, and a combinationthereof.
 19. The electronic device of claim 1, wherein the electronicdevice is configured to emit light having a color gamut ratio of atleast about 87% with respect to BT2020 in a CIE1931 color space.
 20. Theelectronic device of claim 1, wherein the layer is configured such thatgreen light emitted from the photoconversion layer has a colorcoordinate Cy value of greater than or equal to about 0.73.
 21. Theelectronic device of claim 10, wherein the first quantum dot has aquantum yield of greater than or equal to about 50% and the secondquantum dot has a quantum yield of greater than or equal to about 60%.22. The electronic device of claim 10, wherein the first quantum dot isconfigured to show a luminescent peak having a full width at halfmaximum of less than or equal to about 45 nm and the second quantum dotconfigured to show a luminescent peak having a full width at halfmaximum of less than or equal to about 30 nm.